The flexible line is advantageously a flexible pipe as described in the normative documents published by the American Petroleum Institute (API), API 17J and API RP 17B, all well known to one skilled in the art.
This definition equally encompasses the flexible pipes of the unbonded type or of the bonded type.
More generally, the flexible pipe may be a composite collection of the <<bundle>> type comprising at least one fluid transport tube and a set of electric, hydraulic or optical links able to convey electric or hydraulic power or a piece of information, between the bottom and the surface of the expanse of water.
In still another alternative, the flexible line, an umbilical comprising a set of electric and/or optical and/or hydraulic lines able to convey a piece of information, electric power or hydraulic power.
Such flexible lines in the petroleum industry are notably used in deep seas, and frequently extend through an expanse of water between a surface facility and a bottom assembly. These flexible lines may also extend at the bottom of the expanse of water between bottom facilities.
In order to use the flexible lines in these types of applications, it is necessary to reinforce them considering the forces and pressures applied on the line. For this purpose, the flexible pipes generally include, from the inside to the outside, a metal carcass in order to spread out the crushing radial forces, an internal sealing sheath in polymer, for containing the transported fluid, a pressure vault in order to resist the internal pressure of the transported fluid in the internal sheath, and balanced armor plies for spreading the axial tensile loads.
The pipe generally comprises an external sheath in polymer for protecting the whole of the pipe and notably for preventing water from penetrating into its thickness.
The internal carcass and the pressure vault generally consist of wound longitudinal elements, following a short pitch. They impart to the pipe its resistance to radial stresses.
The armor plies often consist of metal profiles wound according to long pitches, in order to spread the axial loads.
The metal armor plies have the disadvantage of being sensitive to corrosion, and to have a large weight.
To overcome this problem, patent application WO 99/49259 of the applicant describes composite armors, made on the basis of carbon fibers.
The armors are formed on the basis of armor elements of the aforementioned type, comprising a plastic matrix in ribbon form and longitudinal carbon fiber filaments, preferably organized as rovings which are embedded in the matrix.
Such a ribbon has highly satisfactory mechanical characteristics, taking into account the high strength and the large chemical inertia of carbon fibers. Further, the cost of carbon fibers is relatively low as compared with that of other fibers.
Such armors are generally very robust and allow the flexible line to be positioned in the expanse of water for very long time periods.
However, in certain cases, it may be desirable to check that the flexible line keeps its integrity, notably just after its facility, and during its use.